This invention relates to an improved method and apparatus for filtering water or wastewater containing suspended solids. The present invention, more specifically, is an improvement over prior art systems for filtering these kinds of wastes. While water and wastewater are referred to as the waste or material to be filtered free of particulates or suspended solids, the present invention is not so limited in use. It effectively treats many other liquid industrial effluents and slurries.
Typical prior art vertical filtration units are disclosed and explained in U.S. Pat. No. 4,060,484, to Austin et al. and U.S. Pat. No. 4,891,142, to Hering, Jr., both of which patents are herein incorporated by reference. The water/wastewater undergoing filtration in these systems moves downward, due to the force of gravity, through the filter media. The filter media, containing different sized grains or particles, usually sand, is dirtied by the suspended solid particles it removes from the water/wastewater undergoing treatment. By the time the water/wastewater reaches the bottom of the filtration chamber, it has been filtered free of suspended solid particles. These solid particles are then carried by the filter media, from which they must be removed.
A mixture of a portion of the filtered water, the now dirtied filter media at the bottom of the filter unit and a small amount of filtered water are then air lifted to a washbox. This lifting is carried out by an air-lift tube equipped with a compressed air supply. The mixture of filtered water, filtration sand, and suspended solids is directed against a baffle or plate, to scrub the suspended solid particles from the sand.
The washed sand is returned to the top of the filter media bed. The suspended solid particles, washed from the filter media, are flushed from the filter by a combination of filter influent and filtered water that carry out the suspended solids across a reject weir.
The filtered water collects inside an internal cylindrical screen at or near the bottom of the filtration unit, from which it is drawn. The filtration cycle automatically repeats itself with the influx of a new supply of water/wastewater to be filtered.
Prior art continuous systems for the filtration of water/wastewater and the removal of suspended solid particles are typically not as effective or efficient, however, as industry and the public need and desire. Standard filtration systems can be effective, i.e., they provide high filtration rates. Even so, they are not as efficient as the present invention. They require pumps and must be taken off-line to clear the dirtied filtration material.
Many of these and other-shortcomings in prior art vertical filtration systems are met by such patented systems as that disclosed in the above-cited Hering, Jr. patent. The present invention, however, provides even further advantages and benefits.
Accordingly, it is an object of this invention to provide an apparatus and process for filtering water/wastewater more efficiently than can be done with presently available air-lift systems.
It is a further object of the present invention to provide a vertical filter, in which the filtering material is constantly and more efficiently circulated and cleaned.
It is still another object of the present invention to provide a vertical flow particulate filtering system that operates as economically as possible, with no moving mechanical parts to malfunction or otherwise require maintenance or replacement.
Other objects and advantages will become apparent from the drawings and specification that follow.